Phylogeny and taxonomy of Synechococcus–like cyanobacteria

Unicellular cyanobacteria constitute a substantial, ecologically important part of freshwater and marine microflora. Solitary, elongated cyanobacterial cells without apparent slime envelopes and dividing in a single plane perpendicular to the longitudinal axis were traditionally classified into the genus Synechococcus. The type species originates from a freshwater benthic habitat while a number of other Synechococcus–like species were described from diverse environments. Morphologically similar, unicellular populations of “Synechococcus” belong to the most abundant oxygen evolving prokaryotes inhabiting freshwater and oceanic picoplanktic communities. Other species from extreme thermal habitats were described from temperatures over 70 °C. Recent molecular analyses, particularly the 16S rRNA gene and other multi–locus gene based phylogenies of Synechococcus–like species reveal the polyphyly and phylogenetic diversity of such simple cyanobacteria emphasizing the necessity of their accurate polyphasic taxonomic re–classification. To better understand the phylogeny of different Synechococcus–like species, we constructed a genome–derived phylogenetic tree using 133 cyanobacterial and eubacterial genomes as well as a 16S rRNA gene phylogenetic tree. Both trees indicate existence of deep splits between individual Synechococcus lineages corresponding with indistinct ecological and cytomorphological differences. The generic units derived from the traditional concept of the genus Synechococcus based on the combined traits and markers must be defined and validly described. The comparative taxonomic classification of phylogenetic clusters corresponding to various morphotypes and genotypes similar to the genus Synechococcus (Cyanobium, Parasynechococcus, Picosynechococcus, Prochlorococcus, Thermosynechococcus, Thermostichus) are discussed in the article

Evolutionary Patterns of Thylakoid Architecture in Cyanobacteria

While photosynthetic processes have become increasingly understood in cyanobacterial model strains, differences in the spatial distribution of thylakoid membranes among various lineages have been largely unexplored. Cyanobacterial cells exhibit an intriguing diversity in thylakoid arrangements, ranging from simple parietal to radial, coiled, parallel, and special types. Although metabolic background of their variability remains unknown, it has been suggested that thylakoid patterns are stable in certain phylogenetic clades. For decades, thylakoid arrangements have been used in cyanobacterial classification as one of the crucial characters for definition of taxa. The last comprehensive study addressing their evolutionary history in cyanobacteria was published 15 years ago. Since then both DNA sequence and electron microscopy data have grown rapidly. In the current study, we map ultrastructural data of >200 strains onto the SSU rRNA gene tree, and the resulting phylogeny is compared to a phylogenomic tree. Changes in thylakoid architecture in general follow the phylogeny of housekeeping loci. Parietal arrangement is resolved as the original thylakoid organization, evolving into complex arrangement in the most derived group of heterocytous cyanobacteria. Cyanobacteria occupying intermediate phylogenetic positions (greater filamentous, coccoid, and baeocytous types) exhibit fascicular, radial, and parallel arrangements, partly tracing the reconstructed course of phylogenetic branching. Contrary to previous studies, taxonomic value of thylakoid morphology seems very limited. Only special cases such as thylakoid absence or the parallel arrangement could be used as taxonomically informative apomorphies. The phylogenetic trees provide evidence of both paraphyly and reversion from more derived architectures in the simple parietal thylakoid pattern. Repeated convergent evolution is suggested for the radial and fascicular architectures. Moreover, thylakoid arrangement is constrained by cell size, excluding the occurrence of complex architectures in cyanobacteria smaller than 2 μm in width. It may further be dependent on unknown (eco)physiological factors as suggested by recurrence of the radial type in unrelated but morphologically similar cyanobacteria, and occurrence of special features throughout the phylogeny. No straightforward phylogenetic congruences have been found between proteins involved in photosynthesis and thylakoid formation, and the thylakoid patterns. Remarkably, several postulated thylakoid biogenesis factors are partly or completely missing in cyanobacteria, challenging their proposed essential roles

A revision of the genus Geitlerinema and a description of the genus Anagnostidinema gen. nov. (Oscillatoriophycidae, Cyanobacteria)

The simple filamentous cyanobacterial genus Geitlerinema is heterogeneous. At least two distinct phylogenetic clades can be derived from the set of most common freshwater Geitlerinema species. Our revision is based on the original description of the type species G. splendidum aka Oscillatoria spendida and on molecular sequencing of morphologically relevant strains. The revised Geitlerinema contains only one species according to morphological similarity with its original description. Consequently, the majority of other freshwater species inferred from molecular sequencing of 16S rRNA gene and 16S–23S ITS analysis (related both genetically and morphologically to G. pseudacutissimum) must be classified as a special taxon on the generic level. The name Anagnostidinema is proposed for this genus, which was selected in memory of the prominent late cyanobacterial specialist Konstantinos Anagnostidis. The genetic position, short review and characteristics of the newly defined genus Anagnostidinema is presented in this paper. The taxonomy of the rest of species (including the marine taxa), which are currently unable to be classified taxonomically with certainty, remain to be resolved in future studies

Phylogeography of the Microcoleus vaginatus (Cyanobacteria) from Three Continents – A Spatial and Temporal Characterization

It has long been assumed that cyanobacteria have, as with other free-living microorganisms, a ubiquitous occurrence. Neither the geographical dispersal barriers nor allopatric speciation has been taken into account. We endeavoured to examine the spatial and temporal patterns of global distribution within populations of the cyanobacterium Microcoleus vaginatus, originated from three continents, and to evaluate the role of dispersal barriers in the evolution of free-living cyanobacteria. Complex phylogeographical approach was applied to assess the dispersal and evolutionary patterns in the cyanobacterium Microcoleus vaginatus (Oscillatoriales). We compared the 16S rRNA and 16S-23S ITS sequences of strains which had originated from three continents (North America, Europe, and Asia). The spatial distribution was investigated using a phylogenetic tree, network, as well as principal coordinate analysis (PCoA). A temporal characterization was inferred using molecular clocks, calibrated from fossil DNA. Data analysis revealed broad genetic diversity within M. vaginatus. Based on the phylogenetic tree, network, and PCoA analysis, the strains isolated in Europe were spatially separated from those which originated from Asia and North America. A chronogram showed a temporal limitation of dispersal barriers on the continental scale. Dispersal barriers and allopatric speciation had an important role in the evolution of M. vaginatus. However, these dispersal barriers did not have a permanent character; therefore, the genetic flow among populations on a continental scale was only temporarily present. Furthermore, M. vaginatus is a recently evolved species, which has been going through substantial evolutionary changes

Phylogeny, Phytogeography, and Taxonomy of Polar Oscillatoriales

Morphological and phylogenetic diversity of 143 strains belonging to Oscillatoriales with focuson traditional genera Phormidium sensu lato and Microcoleus were studied. The 88 strains of Ph. autumnale, Ph. setchelianum, Ph. subfuscum, Ph. favosum etc., and M. vaginatus confirmed the generic identity with typical Microcoleus Desmazi?res ex Gomont. The necessary nomenclatoric transfers were realized defining the revised genus Microcoleus. Based on phylogeny and morphology the taxonomic revision of the Antarctic species Ph. murrayi (Lyngbya murray West & West) was implemented and the genus Wilmottia was established. The phylogenetic evaluation of morpho-species included in Phormidium group I (Ph. lloydianum and Ph. acuminatum Gomont) preceded the definition of species Oxynema thaianum spec. nova. The biogeography of Antarctic and Arctic strains of M. vaginatus (Ph. autumnale) based on 16S rDNA and ITS (internal transcribed spacer of the 16S rDNA -23SrDNA ribosomal operon) sequences and strain's morphology was evaluated. The comparison of polar and non-polar strains indicated that the Antarctic populations of M. vaginatus remained isolated from time of the isolation of the Antarctica from the Gondwana before ~31?45 Ma, whereas the transport of populations within Arctic is relatively frequent even at the present time. It was shown that the polar strains of M. vaginatus from the north and south polar areas were not identical

Insect rearing on biowaste represents a competitive advantage for fish farming

Feeding cost is among the main drivers in the price competitiveness of intensively-fed-aquaculture (IFA) products. As soaring energy prices increase the costs of technologies used to increase the digestibility of plant protein feeds, there is an urgent call for comprehensive knowledge on the mass use of insects as fish feed. This review identifies the key aspects of insect incorporation into established IFA practices and puts them into a commercial context. Larvae of Black soldier fly (BSFL) is identified as the most versatile in terms of (a) variety of biowaste usable for its rearing, (b) automatization and scaling up, (c) nutritional value and (d) circular and environmental aspects. Furthermore, modifications insect diets can increase the levels of valuable compounds such as omega-3 fatty acids in fish. Other insects such as ants or mealworms have the potential to meet the nutritional requirements of various fish species. While today the production costs of BSFL (mostly around 3.5 euro kg(-1)) are mostly determined by labour costs, it is predicted that intensified industrialization of insect rearing could reduce the production cost below 2 euro kg(-1). In addition, multiple positive economic impacts, as well as environmental spillovers, have been identified. It is proposed that further research should be directed towards the refining and further valorization of byproducts from insect farming which could further dissolve the rearing cost. Bringing the IFA into compliance with the principles of the circular economy increases its competitiveness by reducing production costs and improving public opinion